Parents facing marriage breakdowns have cottoned on to a strategy practised by siblings of younger children all over the world — blame it on the baby.

A survey of 2,000 parents found that a third of those who had divorced or separated blamed sleepless or interrupted nights caused by crying children.

Parents of young children were found to get only six hours sleep a night — one hour less than recommended — and the resulting tiredness was found to be damaging to relationships.

The US research showed that a good night’s sleep improved a couple’s relationship by making them less selfish and more likely to be polite to each other.

“Poor sleep may make us more selfish as we prioritize our own needs over our partners,” University of Berkeley, California psychologist Amie Gordon said.

Eleven per cent of parents admitted to pretending to be asleep when their child woke up so their partner would have to deal with them, while another 11 per cent they would shut the door to block out the noise.